Treatment of hydrocarbon oils



Patented Nov. 13, 1934 UNITED STATES ATENT @FFICE TREATMENT OFHYDROCARBON OILS No Drawing.

Application May 21, 1931,

Serial No. 539,140

12 Claims.

This invention relates to the treatment of hydrocarbon oils and refersmore particularly to the treatment of the lighter portions of crudepetroleums produced either by straight run distillation methods or bythe cracking of heavier residues to produce lighter fractions.

In a more specific sense the invention contemplates the treatment ofrelatively low boiling petroleum fractions by reagents capable ofremoving sulphur therefrom, specific methods and agents being disclosedwhich offer distinct improvements and advantages over the methods at thepresent time employed in oil refining in that they are more specificallydirected toward the elimination of types of sulphur compoundsparticularly resistant to the action of the more readily availabletreating reagents such as sulphuric acid, plumbate solutions, metals andtheir oxides and many other treating agents.

Many types of sulphur compounds have been identified in the fractions ofcrude petroleums, representatives of the following groups having beenfound in large amounts: mercaptans, sulphides, disulphides, thiophenes,thiophanes, compounds of the sulfoxy type containing both sulphur andoxygen and heterocyclic bodies containing both sulphur and nitrogen.

In the ordinary methods of refining petroleum distillates with sulphuricacid of varying concentration, the total sulphur content is reducedincidental to the production of finished distillates freed sufficientlyfrom highly unsaturated organic derivatives to render them stable tooxidizing influences and capable of holding their color and otherdesirable properties in storage. To reduce the sulphur content below acertain point requires excessive amounts of sulphuric acid or otherreagents, the reason being that the sulphur is combined in ringcompounds of the thiophene or thiophane type and these compounds areless reactive than other groups of compounds, for example, compounds ofthe mono-olefinic type or the partially saturated closed-ringhydrocarbons. The reduction of sulphur content to a negligible pointwithout removal of desirable hydrocarbons has been the object of muchstudy and experimentation and it is the object of the present inventionto disclose a method of treatment whereby this may be accomplished.

In one specific embodiment the invention comprises treating petroleumdistillates after easily removable sulphur compounds have been treatedout with commoner reagents, with halogens and the hydrogenatedderivatives of such organic nitrogen compounds as pyridine, pyrrole,etc.,

the ring sulphur compounds being split up by this reaction with theliberation of sulphur as hydrogen sulphide and the formation of highmolecular weight nitrogen compounds of a mixed type.

The most typical of the hydrogenated compounds Which may be employed inthe desulphurizing reactions is piperidine or pentamethyleneimine, thissubstance being produced by the direct hydrogenation of pyridine by anyconvenient method such, for example, by reduction with sodium inalcohols or the direct hydrogenation in the presence of reduced metalssuch as nickel or other active hydrogenating catalysts Piperidine has aboiling point of 222 F. and is readily soluble in water and alcohols andto a limited but suifioient extent in mineral oil distillates which itis desired to desulphurize.

As the reactions comprised within the present invention arecharacteristic of the pyridine homologous series, the case of piperidineis merely cited as being that of a type compound since the nitrogenbases employed after suitable hydrogenation may be any of those obtainedfrom such sources as bone oil or coal tar, or from the weak acidextraction of portions of crude petroleums that are particularly rich insuch nitrogen compounds, such as, for example, are obtained from certainCalifornia petroleums. In the last named case, nitrogen containingdistillates may be extracted with, for example, Weak sulphuric acid of15 to 20% concentration, the nitrogen bases liberated by neutralizationof the acid with alkalies such as caustic soda or lime and the mixtureof nitrogen compounds liberated hydrogenated by any suitable means torender them of a constitution necessary for the desulphurizingreactions.

It has been found also that the reactions of decomposition of thethiophene nucleus are best brought about following the attachment of atleast one atom of halogen to the ring and it has also been found thatthe desired desulphurizing reactions occur under the least severeconditions of temperature and pressure when iodine is the halogen atom.Heterocyclic ring compounds containing sulphur are more reactive withhalogens than the corresponding cyclic compounds containing no sulphurin the ring. The addition of halogens to the ring sulphur compounds maybe accelerated by the presence of minor amounts of suitable catalyticsubstances. In the case of chlorine, the presence of finely divided ironor aluminum or their chlorides has been found to speed upthehalogenating reactions and in the case of bromine and iodine goodresults have been obtained in the presence of minor amounts of mercuricoxide.

The reactions of thiophene with hydrogenated nitrogen bases of thepyridine type are typified by the following structural equation:

tiff-("3H C) C l Cg C I +2NH'C5HH):H[+H7S+ CH CH 1 l S NCsHn! aHzoIodotliiophene Piperi- Elydriodic Hydrogen Heavy nitrogen done acidsulphate base It will be evident from the consideration of the nature ofthe above reaction that it would be facilitated by the presence ofexcess of base or such alkalies as caustic soda, ammonia, etc., whichwould tend to absorb the halogen acid and hydrogen sulphide resultingfrom the reaction and such has been found to be the case. It will alsobe evident that the reaction is novel in regard to the fact that thesulphur contained in the thiophene ring has been completely removed ashydrogen sulphide, and that therefore the reaction given above appliedto the residual sulphur compounds in petroleum distillates will effecttheir substantially complete decomposition with the reduction of thesulphur content of the distillates to a negligible point.

The halogen necessary for further reactions may be regenerated from thehalogen acid or the salt by any suitable means such as the electrolysisof the salt and it is convenient to recover the nitrogen base necessaryto the main reaction by the heat treatment of the heavy polymerizednitrogen bodies which results in their decomposition into lighterfractions. The process may be therefore made completely regenerative andcyclic.

The reactions characteristic of the invention may be brought about in avariety of ways and in a variety of different types of equipment. someof which will be briefly described. A distillate from which it isdesired to remove thiophene sulphur may be caused to circulate from thebottom cone of an agitator back into the top through distributing means,proper amounts of halogen being added as the oil is circulated and inthe case of iodine or bromine, certain minimum amounts of mercuricoxide. Chlorine may be passed in as a gas in the presence of finelydivided iron or aluminum or their anhydrous chlorides. The solidsubstances may be introduced into the circulating pump as concentrates,slurries or suspensions in small amounts of the oil undergoing treatmentor they may be gradually added to the body of oil in the agitator andbecome mixed with the oil during circulation, the amounts being minorand causing no trouble in operation. After this preliminary halogenatingtreatment, any solid materials may be removed by settling anddecantation of the liquid or the final traces may be removed byfiltering through porous media such as sand filters, fullers earth.porous plates. etc.

The following desulphurizing reactions with piperidine commonly requiresuperatmospheric temperatures and may be conveniently brought aboutprior to the redistillation of the treated oil by introducing thereagent into the stream of oil entering a tubular heating element inwhich sufficient heat is being added to enable the subsequentvaporization of the oil with the separation of light fractions of motorfuel boiling point range, the high molecular weight nitrogen compoundsbeing recovered as a residue from the refiuxes in the fractionatingtower and the traces of hydrogen sulphide in the overhead distillatebeing removed by a light alakli soda treatment.

Kerosene may be substantially completely desulphurized in a similarmanner, it being at times unnecessary to redistill the treated oil asthe hydrogen sulphide and halogen acid may be removed by relativelyminor treatments with caustic soda or other alkalies and the nitrogenbases removed by comparatively light acid treatment.

The process of the invention is readily adaptable to the treatment ofhydrocarbon oil vapors such as those coming from the fractionator of acracking plant, and may be used as a step in conjunction with othertreatments that may be conducted upon such vapors prior to theircondensation. For example, such vapors may be subjected to preliminarytreatments for desulphi. ng and other refining effects such astreatments with solid metallic or adsorbent contact materials ormiscellaneous chemical treating reagents such as acid, alkaline or saltsolutions and then the process peculiar to the present inventionutilized to substantially rid the vapors of thiophene or cyclic sulphurcompounds, this step being followed by further treatments or washings toefiect the removal of hydrogen sulphide and acid reaction products, andfinal rectification to produce a treated end-point gasoline.

As an example of the results obtainable by a treatment comprised withinthe scope of the invention, a cracked pressure distillate produced froma California residuum by cracking the same under superatmospherictemperature and pressure may be found to contain sulphur to the extentof 0.5%. Treatment with caustic soda may effect the removal of dissolvedhydrogen sulphide and certain of the more reactive mercaptans so thatthe sulphur content is reduced to approximately 0.4%. Further treatmentwith 66 Be. sulphuric acid in amounts equivalent to '7 lbs. per barrelof oil may still further reduce the sulphur content to 0.2%, reductionbelow this point by the use of larger amounts of acid being accompaniedby undesirable losses of material.

To eliminate the 0.2% sulphur still remaining, the oil may be treatedwith a small amount of chlorine in the presence of ferric chloride, theamount used being approximately equivalent to the amount of sulphurpresent or pound of chlorine per barrel. This chlorination may beeffected at ordinary temperatures by circulation from and to an ordinaryagitator as already mentioned. To sheet the final desulphurization thetreated oil may be continuously fed to a tubular heating element and anamount of hydrogenated nitrogen bases of the piperidine type equivalentto approximately pound per barrel admitted to the suction side of thepump. There may be also added a small amount of ammonia or other alkaliand the mixture of oil and treating reagents elevated to a suitabletemperature during passage through the coil. this temperature, forexample, being usually within the range of 400 to 600 F., 500 F. beingmany times sufiicient to produce substantially completedesulphurization. The heated products may be discharged into a suitabletower and overhead fractions of gasoline boiling point range producedwhich upon light caustic treatment to neutralize traces of acidic andsulphur compounds may be found to contain as low as 0.01% sulphur.

The foregoing description has indicated that the invention comprises aprocess of the substantial desulphurization of petroleum distillates bynew and novel means, but the particular example cited is only one ofmany and as such is not to be construed in a limiting sense on the broadscope of the invention.

By the term heterocyclic nitrogen compound employed in the claims, Imean a ring compound containing nitrogen in the ring.

I claim as my invention:

1. A method of treating hydrocarbon oil to remove heterocyclic sulphurcompounds therefrom which comprises, mixing a halogen selected from thegroup consisting of chlorine, bromine and iodine with said oil in thepresence of a catalyst, and subjecting the resulting mixture in companywith a homologue of piperidine to a relatively elevated temperature.

2. A method of treating hydrocarbon oil to remove sulphur compounds ofthe thiophene type therefrom which comprises, mixing a halogen selectedfrom the group consisting of chlorine, bromine and iodine with said oilin the presence of a catalyst, and subjecting the resulting mixture incompany with a compound selected from piperidine and its homologues to arelatively elevated temperature.

3. Steps in a process of desulphurizing hydrocarbon oil which comprises,mixing a halogen selected from the group consisting of chlorine, bromineand iodine with said oil in the presence of a catalyst, passing saidmixture in company with a heterocyclic organic nitrogen compound andalkali to a heating zone wherein the same is raised to a relativelyelevated temperature, said compound being selected from the groupconsisting of piperidine and its homologues.

4. In the desulphurization of hydrocarbon oils, the method of removingring sulphur compounds which comprises treating the oil with a halogenselected from the group consisting of chlorine, bromine and iodine andan organic nitrogen base selected from the group consisting ofpiperidine and its homologues.

5. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and a hydrogenatedderivative of a heterocyclic nitrogen compound containing at least fivemembers in the ring.

6. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and a hydrogenatedderivative of pyridine.

7. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and a hydrogenatedderivative of pyrrole.

8. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and piperidine.

9. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and then heating the oil inthe presence of a hydrogenated derivative of a heterocyclic nitrogencompound containing at least five members in the ring.

10. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and then heating the oil inthe presence of alkali and a hydrogenated derivative of a heterocyclicnitrogen compound containing at least five members in the rlng.

11. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and thereafter heating theoil in the presence of a hydrogenated derivative of pyridine.

12. In the desulphurization of hydrocarbon oils, the method whichcomprises treating the oil with a halogen selected from the groupconsisting of chlorine, bromine and iodine, and thereafter heating theoil in the presence of a hydrogenated derivative of pyrrole.

RICHARD F. DAVIS.

